In internal combustion engines, particularly in four-stroke engines, the cycle is carried out in two rotations of the crankshaft. This uses the traditional link arm-crank system, which requires a full descent and return of the piston for a full turn to occur with a single rotation of the crankshaft. This situation leads to irregularities in the transferred torque and to stray inertial forces. These actions disrupt the balance of the engine.
A 0.5 reduction in ratio should be introduced in the transmission from the crankshaft rotation to the cam-shafts so as to assure proper distribution. This process, however, complicates engine kinematics, thus weakening the engine itself.
For a pre-determined number of cylinders, the power supplied is limited by the maximum inertial forces which can be supported by the pistons. Moreover, the effort to raise the power-to-weight ratio by increasing crankshaft rotation speed necessitates the addition of a substantial reduction mechanism, taking into account rotation speeds to be transferred to the wheels. This leads to rapid cylinder and piston wear.
Rapid engines require close and constant supervision of the number of crankshaft rotations. It must be taken into account that, as described above, during high speeds of operation, the link arm and pistons are quite close to the point of breaking down; high output is obtained at this cost.
A mechanism allowing a four-stroke engine to perform a cycle in a single rotation of the crankshaft is already known (French Patent Request No. 2,622,251). The aim of this mechanism is to increase the output of internal combustion engines and to simplify their construction. Its principal features are its orbital link arm, mounted on the oblique crankpin of a crankshaft, attached to the piston with an auxiliary link arm. Operation of this system requires replacing the classical rotation pin, joining the piston to the link arm with a swivel joint allowing orbital displacement of the auxiliary link arm. This complicates the structure, weakens the bond between the link arm and the piston and generates considerable cyclic end thrusting on the crankshaft. This can cause vibrations which are detrimental to the performance of the crankshaft bearings.
The object of this invention is to overcome these disadvantages. This invention, in its present form, resolves the problem of creating a new system for transforming linear piston displacement in an internal combustion engine to shaft rotation, thus allowing the association of two descents and returns of a piston with a single rotation of the shaft.